1. Technical Field
The present invention relates to a probe for detecting a mutation, a method of detecting a mutation, a method of evaluating the efficacy of a drug, and a kit for detecting a mutation.
2. Related Art
One of the causes for the onset of lung cancer is a gene mutation. Therefore, there is an ongoing effort to identify a gene that is thought to be associated with the onset of lung cancer. Examples of such a gene mutation that is believed to be associated with the onset of lung cancer include an EGFR gene mutation and an ALK gene mutation.
The ALK (Anaplastic Lymphoma Kinase) gene encodes a receptor tyrosine kinase and is known to be fused with the EML4 gene when an inversion occurs in the second chromosome. It is believed that a constitutively activated tyrosine kinase is produced by the work of this fusion gene (EML4-ALK), inducing the onset of lung adenocarcinoma. Thus, the use of an ALK inhibitor has been tried in the field of lung cancer treatment. As such an ALK inhibitor, crizotinib is known.
However, although crizotinib has been observed to have a certain therapeutic effect in early stages, the effect of this agent may be gradually reduced more than expected.
It has been discovered that the expression of such an inhibitory activity is associated with two mutations occurring in the EML4-ALK gene, namely a mutation in which the 1156th cytosine in the amino acid sequence of the ALK gene is substituted with tyrosine (hereinafter, sometimes referred to as “ALK(C1156Y)”) and a mutation in which the 1196th leucine in the amino acid sequence of the ALK gene is substituted with methionine (hereinafter, sometimes referred to as “ALK(L1196M)”) (see the New England Journal of Medicine, Vol. 363, pp. 1734-1739, (2010)). It has been proven that these gene mutations show a common property in that they occur at the crizotinib-binding pocket site in the EML4-ELK fusion gene and consequently alter the shape of the binding pocket to reduce the binding affinity between crizotinib and the EML4-ALK fusion gene. Accordingly, in the use of an ALK inhibitor, it is important to detect the presence or absence of these ALK gene mutations as a factor for predicting the effect of the ALK inhibitor.
Meanwhile, in recent years, melting curve analysis (Tm analysis) has been utilized for a test for detecting a gene mutation. In this method, after amplifying a mutation-containing region by a PCR method, a melting curve analysis is performed using a nucleic acid probe labeled with a fluorescent dye so as to analyze a mutation in a base sequence based on the results of the melting curve analysis (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2002-119291).